How to set the focus to a child window without refreshing it?

Now when click on a link, it opens a popup window, which contain a data entry form, I entered some information into that form. Then I need to review other information, from other popup window, so I go back to the main window, click on another link, a new popup window get open which contain the information I need to review. I get the information and close this popup window, so now I am on the main window, then again I click on the link for that data entry form, so the popup window comes up but I lost the information that I have entered, that's because I am relodiing the popup window once again.

Let us see how it works,

• When attempt to open the window again with the same name in the second parameter of the windows open method, you will to get the windows handle. If the window is already open, it will return the handle of the opened window or it will open a new window and return it's handle
• The first parameter (the url) is passed as an empty string, so the page will not get redirected which will result in the contents of the window remaining unchanged.

Note : You cannot get the handle if the page is not on the same host as its opener